[Heathkit] AT-1 Question

Fri, 23 Jan 2004 05:32:23 -0500

  Some experiments here indicate the link coupling, if done
rather loosely  such as at the cold end of the tank provides about
20 dB at the second harmonic. A far cry from a pi-network, but
if the link output is run into an 50 ohm I/O output filter then
the performance is pretty good. So you could preserve the AT-1 by 
just running it into a 50 ohm I/O pi network, or even better a half wave
filter. But you'd have to build a filter for each band you intend to
operate.
 I've built critical coupled link outputs feeding half wave filters here 
while prototyping no-tune amplifiers and 60-65 dB at the second
harmonic was obtainable without much trouble.

Mark  WB8JKR

On Thu, 22 Jan 2004 23:03:06 -0500 Garey Barrell <[email protected]>
writes:
> Joe -
> 
> The link coupled output does NOT have the harmonic suppression 
> provided by a 
> Pi-Net.  I used to have typical numbers, but long forgotten!  :-)
> 
> That said, it is pretty difficult to match anything but a resonant 
> antenna with 
> link coupling, so you usually end up with an antenna tuner anyway!  
> The Heath 
> AC-1 was offered by Heath to address this need, but it cost half as 
> much as the 
> transmitter, so most (poor!) hams just kludged something together. 
> With the 
> result that the AC-1 is even more scarce today than the AT-1.  The 
> AC-1 included 
> a low pass filter AND and LC matching network AND a neon "output 
> indicator".
> 
> 73, Garey - K4OAH
> Atlanta
> 
> 
> 
> [email protected] wrote:
> 
> > It appear the AT-1 has a link coupled output.  What is the 
> harmonic 
> > suppression characteristics compared to a pi-section output?
> > 
> > Thanks,
> > Joe
> > 
> > 
> 
> 
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